A typical system for paving a work area such as a parking lot or road can include numerous different machines. Supply machines such as haul trucks may be used to deliver paving material for distribution and compaction on a work surface. Paving machines may be supplied directly from the haul trucks, or from material transfer vehicles. Paving machines typically distribute paving material and perform a preliminary compaction of a “mat” of paving material with a screed mounted at the back end of the paving machine. In many systems, the paving machine is followed relatively closely by a compacting machine known in the art as a breakdown roller. Another compacting machine known as an intermediate roller often follows the breakdown roller, and a final finish roller may follow behind the intermediate roller in some systems. Various factors can affect the efficiency and success of a paving job, such as operator experience with the various machines, environmental conditions and temperature of the paving material at different stages of the paving process. Working paving material under optimum temperature conditions has long been recognized as important, but has heretofore been difficult to ensure and verify without manual measurements by support personnel.
Paving material is typically obtained at a relatively high temperature at an asphalt plant. Depending in part upon the distance a supply machine has to travel to reach a work site, traffic, ambient temperature, etc., the asphalt can cool somewhat prior to delivery. Progress of the paving machines and compactors can also vary, and haul trucks may have to wait to offload the paving material if paving has slowed. The manner in which paving material is delivered to a paving machine can also vary among systems, e.g. via a material transfer vehicle or “MTV” versus direct delivery from a haul truck. Due to the variables which can affect the timing of the various events in a paving process, temperature of the paving material when it eventually reaches the paving machine can be at least somewhat unpredictable. Once transferred into a paving machine, paving material will tend to cool further prior to its being distributed onto a work surface. The extent of cooling once within the paving machine can vary depending on the temperature of paving material at delivery, environmental factors, proper versus improper operation of the paving machine, etc. In some instances, paving material may segregate within a paving machine, and thus relatively cooler and relatively warmer pockets of material within the machine may exist, leading to unexpected temperature gradients in the paving material once distributed on the work surface. When paving material is finally discharged and distributed by the paving machine, treated via its screed, and ready to be compacted by the various compacting machines, its temperature can vary significantly from an expected temperature, and may even be non-uniform from one paved region to the next due to unintended segregation or poor mixing. As alluded to above, being able to work paving material under certain conditions such as optimum temperature can often be of paramount importance.
For example, depending upon the particular mix of paving material, it may have a temperature range known in the art as the “tender zone” where attempted compacting is unlikely to succeed. When paving material is in the tender zone it is prone to shoving and there may be a “wave” in front of the compactor drum. It is well known in the paving arts that successful compaction may take place when the paving material temperature is either above the tender zone or below the tender zone, but not within the tender zone. Ideally, breakdown rollers, mentioned above, follow the paving machine closely enough that they compact paving material prior to its cooling to the tender zone. Intermediate rollers typically follow sufficiently far behind the breakdown roller that the paving material has cooled below the tender zone by the time the intermediate roller reaches a particular stretch of paving material. It is also typically desirable to employ the finish roller prior to paving material cooling to a point at which it becomes too hard.
For most paving systems, there is thus at least a rough theoretical relative timing between the various paving activities, such as paving versus compacting, which can be expected to result in optimum paving quality. Engineers have recognized for some time that paving material composition, environmental conditions, machine speed and spacing, and other variables can make predicting a temperature for paving material at a particular time challenging. While manual measurements or estimates of time, air temperature, asphalt temperature, wind speed, humidity, cloud cover, and other factors can be used in decision making, machine operators and paving site managers still rely to a great extent on experience and guesswork in managing operations.
In addition to the challenges to successfully paving in the first place, many jurisdictions now mandate logging data relating to paving material temperature and machine activities during a paving operation. Records of such operations at a paving site allow paving contractors to establish that paving was performed within specifications, and are commonly related to contract validation and bonuses as well as predictive and forensic aspects of construction. Standard procedure for this type of data logging has heretofore relied principally on manual observation and recording of the temperature of paving material while working a particular area.
One strategy directed at improving operation and efficiency of paving equipment is known from U.S. Pat. No. 6,749,364 to Baker et al. (“Baker”). In Baker's approach, a pavement temperature monitoring system is used on a paver vehicle and sends signals to a display device generating a graphical image of a formed material mat temperature profile. Based on the displayed temperature profile, operational parameters of the paver vehicle or compactor vehicle are purportedly adjusted to provide an acceptable formed mat. Baker's technique may be superior to certain earlier systems and manual approaches to analyzing temperature and adjusting operation, however, there remains ample room for improvement.
The present disclosure is directed to one or more of the problems or shortcomings set forth above.